A bomb hidden in a briefcase exploded in a crowd of people outside the High Court in New Delhi, killing 11 people.

An injured girl is taken to safety after the explosion (Picture: Reuters)

The bomb, the deadliest attack in Indiaâs capital in three years, left a deep crater on the road and shook the building, sending lawyers and judges fleeing outside.

A Muslim militant group claimed responsibility in an email, but investigators said it was too early to name any group as suspects.

The blast, which also injured 59 people at the courthouse gates, was the second to target the building in five months.

âThere was smoke everywhere. People were running and shouting. There was blood everywhere,â said lawyer Sangeeta Sondhi who was parking her car near the gate.

The attack renewed criticism ofÂ Indiaâs ability to protect its main institutions despite a security overhaul that followed the 2008 Mumbai siege. Prime minister Manmohan Singh, who was visiting neighbouring Bangladesh, said: âWe will never succumb to the pressure of terrorists.

âThis is a long war in which allÂ political parties and all the people of India will have to stand united so that this scourge of terrorism is crushed.â

The bomb exploded near a line of more than 100 people waiting for passes to enter the building. Officials said the identities of the dead and injured were not available, but no judges were among the victims.

People ran to the blast site to assist the injured, piling them into auto-rickshaws to take them to hospital.

Ambulances and forensic teams attended the scene along with sniffer dogs and a bomb disposal unit.

Police searched hotels, railway stations and the airport for suspects.